Arabic graffiti has been found daubed on panels covering fuel tanks of easyJet planes at French airports.

An investigation is being carried out into who made the inscriptions, which were written on four planes in France.

The airports cannot be identified for security reasons.

Lisa King, easyJet cabin safety manager, alerted company employees to the graffiti with an email informing them of the discovery of "four aircraft in France with written inscriptions on the inside of the fuel panel, and toilet door in Arabic script."

Philip Baum, editor of Aviation Security International, told The Sun: "Graffiti in itself won't hurt anybody. But the ability of anyone to place a prohibited item near fuel tanks is a concern, of course."

"We know there are people working in restricted areas of airports with extremist sympathies."